pretty format terms in errors

lib/elixir/lib/exception.ex

@@ -177,6 +177,19 @@ defmodule Exception do
     end
   end
 
+  @doc false
+  @spec _format_message_with_term(String.t(), any) :: String.t()
+  def _format_message_with_term(message, term) do
+    inspected =
+      term
+      |> inspect(pretty: true)
+      |> String.split("\n", trim: true)
+      |> Enum.map(&("    " <> &1))
+      |> Enum.join("\n")
+
+    message <> "\n\n" <> inspected
+  end
+
   @doc """
   Attaches information to exceptions for extra debugging.
 
@@ -1431,7 +1444,10 @@ defmodule BadStructError do
 
   @impl true
   def message(exception) do
-    "expected a struct named #{inspect(exception.struct)}, got: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "expected a struct named #{inspect(exception.struct)}, got:",
+      exception.term
+    )
   end
 end
 
@@ -1451,7 +1467,10 @@ defmodule BadMapError do
 
   @impl true
   def message(exception) do
-    "expected a map, got: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "expected a map, got:",
+      exception.term
+    )
   end
 end
 
@@ -1470,7 +1489,10 @@ defmodule BadBooleanError do
 
   @impl true
   def message(exception) do
-    "expected a boolean on left-side of \"#{exception.operator}\", got: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "expected a boolean on left-side of \"#{exception.operator}\", got:",
+      exception.term
+    )
   end
 end
 
@@ -1492,7 +1514,10 @@ defmodule MatchError do
 
   @impl true
   def message(exception) do
-    "no match of right hand side value: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no match of right hand side value:",
+      exception.term
+    )
   end
 end
 
@@ -1518,7 +1543,10 @@ defmodule CaseClauseError do
 
   @impl true
   def message(exception) do
-    "no case clause matching: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no case clause matching:",
+      exception.term
+    )
   end
 end
 
@@ -1548,7 +1576,10 @@ defmodule WithClauseError do
 
   @impl true
   def message(exception) do
-    "no with clause matching: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no with clause matching:",
+      exception.term
+    )
   end
 end
 
@@ -1598,7 +1629,10 @@ defmodule TryClauseError do
 
   @impl true
   def message(exception) do
-    "no try clause matching: #{inspect(exception.term)}"
+    Exception._format_message_with_term(
+      "no try clause matching:",
+      exception.term
+    )
   end
 end
 
@@ -2160,7 +2194,10 @@ defmodule KeyError do
           "make sure to add parentheses after the function name)"
 
       true ->
-        message <> " in: #{inspect(term, pretty: true, limit: :infinity)}"
+        Exception._format_message_with_term(
+          message <> " in:",
+          term
+        )
     end
   end
 

lib/elixir/test/elixir/exception_test.exs

@@ -701,33 +701,34 @@ defmodule ExceptionTest do
       message = blame_message(%{first: nil, second: nil}, fn map -> map.firts end)
 
       assert message == """
-             key :firts not found in: %{first: nil, second: nil}. Did you mean:
+             key :firts not found in:\n\n    %{first: nil, second: nil}. Did you mean:
 
                    * :first
              """
 
       message = blame_message(%{"first" => nil, "second" => nil}, fn map -> map.firts end)
 
-      assert message == "key :firts not found in: %{\"first\" => nil, \"second\" => nil}"
+      assert message == "key :firts not found in:\n\n    %{\"first\" => nil, \"second\" => nil}"
 
       message =
         blame_message(%{"first" => nil, "second" => nil}, fn map -> Map.fetch!(map, "firts") end)
 
-      assert message == "key \"firts\" not found in: %{\"first\" => nil, \"second\" => nil}"
+      assert message ==
+               "key \"firts\" not found in:\n\n    %{\"first\" => nil, \"second\" => nil}"
 
       message =
         blame_message([first: nil, second: nil], fn kwlist -> Keyword.fetch!(kwlist, :firts) end)
 
       assert message == """
-             key :firts not found in: [first: nil, second: nil]. Did you mean:
+             key :firts not found in:\n\n    [first: nil, second: nil]. Did you mean:
 
                    * :first
              """
     end
 
     test "annotates key error with suggestions for structs" do
       message = blame_message(%URI{}, fn map -> map.schema end)
-      assert message =~ "key :schema not found in: %URI{"
+      assert message =~ "key :schema not found in:\n\n    %URI{"
       assert message =~ "Did you mean:"
       assert message =~ "* :scheme"
     end

lib/elixir/test/elixir/kernel/raise_test.exs

@@ -450,16 +450,20 @@ defmodule Kernel.RaiseTest do
     end
 
     test "badmatch error" do
-      x = :example
-
       result =
         try do
-          ^x = Process.get(:unused, 0)
+          [] = Range.to_list(1000_000..1_000_009)
         rescue
           x in [MatchError] -> Exception.message(x)
         end
 
-      assert result == "no match of right hand side value: 0"
+      assert result ==
+               """
+               no match of right hand side value:
+
+                   [1000000, 1000001, 1000002, 1000003, 1000004, 1000005, 1000006, 1000007,
+                    1000008, 1000009]\
+               """
     end
 
     test "bad key error" do
@@ -479,7 +483,7 @@ defmodule Kernel.RaiseTest do
           x in [KeyError] -> Exception.message(x)
         end
 
-      assert result == "key :foo not found in: %{}"
+      assert result == "key :foo not found in:\n\n    %{}"
     end
 
     test "bad map error" do
@@ -490,7 +494,7 @@ defmodule Kernel.RaiseTest do
           x in [BadMapError] -> Exception.message(x)
         end
 
-      assert result == "expected a map, got: 0"
+      assert result == "expected a map, got:\n\n    0"
     end
 
     test "bad boolean error" do
@@ -501,7 +505,7 @@ defmodule Kernel.RaiseTest do
           x in [BadBooleanError] -> Exception.message(x)
         end
 
-      assert result == "expected a boolean on left-side of \"and\", got: 1"
+      assert result == "expected a boolean on left-side of \"and\", got:\n\n    1"
     end
 
     test "case clause error" do
@@ -516,7 +520,7 @@ defmodule Kernel.RaiseTest do
           x in [CaseClauseError] -> Exception.message(x)
         end
 
-      assert result == "no case clause matching: 0"
+      assert result == "no case clause matching:\n\n    0"
     end
 
     test "cond clause error" do
@@ -550,7 +554,7 @@ defmodule Kernel.RaiseTest do
           x in [TryClauseError] -> Exception.message(x)
         end
 
-      assert result == "no try clause matching: :example"
+      assert result == "no try clause matching:\n\n    :example"
     end
 
     test "undefined function error as Erlang error" do

lib/elixir/test/elixir/kernel/with_test.exs

@@ -153,7 +153,7 @@ defmodule Kernel.WithTest do
   end
 
   test "else conditions with match error" do
-    assert_raise WithClauseError, "no with clause matching: :error", fn ->
+    assert_raise WithClauseError, "no with clause matching:\n\n    :error", fn ->
       with({:ok, res} <- error(), do: res, else: ({:error, error} -> error))
     end
   end

lib/elixir/test/elixir/keyword_test.exs

@@ -70,11 +70,11 @@ defmodule KeywordTest do
     assert Keyword.replace!([a: 1, b: 2, a: 3, b: 4], :a, 1) == [a: 1, b: 2, b: 4]
     assert Keyword.replace!([a: 1, b: 2, c: 3, b: 4], :b, :new) == [a: 1, b: :new, c: 3]
 
-    assert_raise KeyError, "key :b not found in: []", fn ->
+    assert_raise KeyError, "key :b not found in:\n\n    []", fn ->
       Keyword.replace!([], :b, :new)
     end
 
-    assert_raise KeyError, "key :c not found in: [a: 1, b: 2, a: 3]", fn ->
+    assert_raise KeyError, "key :c not found in:\n\n    [a: 1, b: 2, a: 3]", fn ->
       Keyword.replace!([a: 1, b: 2, a: 3], :c, :new)
     end
   end

lib/elixir/test/elixir/map_test.exs

@@ -225,11 +225,11 @@ defmodule MapTest do
     assert Map.replace!(map, :b, 10) == %{c: 3, b: 10, a: 1}
     assert Map.replace!(map, :a, 1) == map
 
-    assert_raise KeyError, ~r/key :x not found in: %{.*a: 1.*}/, fn ->
+    assert_raise KeyError, ~r/key :x not found in:\n\n    %{.*a: 1.*}/, fn ->
       Map.replace!(map, :x, 10)
     end
 
-    assert_raise KeyError, "key :x not found in: %{}", fn ->
+    assert_raise KeyError, "key :x not found in:\n\n    %{}", fn ->
       Map.replace!(%{}, :x, 10)
     end
   end